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Sweet Wormwood—Repurposing an Herb for COVID-19?

The battle against COVID-19 has given rise to a new era of global scientific cooperation, with vaccines and antiviral treatments being created at unprecedented speeds.

But amidst all the radical new developments, work has been underway to repurpose a natural treatment known for centuries—Artemisia annua, also known as sweet wormwood.

President Rajoelina.   ©Mmalembo/Wikimedia Commons
President Rajoelina. ©Mmalembo/Wikimedia Commons

In 2020, controversy arose when Madagascar President Andry Rajoelina announced that the African island nation was promoting a drink containing artemisia plant extracts to combat coronavirus.

The World Health Organization quickly rejected that idea, saying there was no proof of artemisia’s effectiveness. But a team of scientists set about trying to understand if one of the plant’s ingredients could indeed have an impact. They were astounded by the results.

Early promise

Sweet wormwood.   ©Jorge Ferreira/Wikimedia Commons
Sweet wormwood. ©Jorge Ferreira/Wikimedia Commons

In May 2021, researchers from Worcester Polytechnic Institute (WPI), Columbia University, and the University of Washington found that extracts from the leaves of the Artemisia annua (A. annua) plant, a medicinal herb also known as sweet wormwood, inhibited the replication of the COVID-19 virus and two of its variants.

Artemisia annua has been studied extensively and used safely for more than 2,000 years in traditional medicine—particularly in China—to treat a variety of fever-related ailments, as well as relieve pain.

The active ingredient found in the dried leaves of Artemisia annua is called artemisinin and works against malaria.

But strangely, the team found that extracts of the plant were more effective when artemisinin levels were low, indicating that it may be another of the plant’s so-far-unidentified compounds that was fighting the virus.

One of the team members, WPI Biology and Biotechnology Prof. Pamela Weathers, has long studied different strains of artemisia, which are grown around the world.

She told The Earth & I that it was a research paper from 2005 about Artemisia annua’s effectiveness against SARS—another coronavirus which spread throughout the Far East in 2002—that originally piqued her interest.

“I knew that Artemisia annua had a lot of antiviral activity from prior reports that focused on artemisinin,” she said. “I searched the literature to see if there were any reports of anti SARS-CoV activity. There was one indicating efficacy.”

Due to the COVID-19 lockdowns at the time, getting back in the lab to start testing their theories was easier said than done for the team.

“We got permission to reopen our lab to prepare extracts for testing,” she said. “All labs had been closed as a pandemic precaution. Two alumni from WPI connected us with the Columbia University Aaron Diamond Research Center where virus testing could be done. That lab works on nasty viruses like HIV and SARS-CoV-2.”

Professor Pamela Weathers holding a sweet wormwood plant.   ©WPI
Professor Pamela Weathers holding a sweet wormwood plant. ©WPI

Once back in the lab, the researchers gathered dried leaves of A. annua from four continents, soaked them in hot water, and tested the solutions against the original SARS-CoV-2 and two variants originating from the United Kingdom and South Africa.

Some leaf samples were twelve years old, but they were still effective against the virus. Researchers also tested artemisinin alone against the viruses, but they found that the plant extracts were more potent. Artemisinin is a compound naturally produced by the plant, but is usually extracted, chemically modified, and developed in combination with other drugs to treat malaria.

Results showed that the extracts of A. annua did not block the virus from entering cells, but they could interfere with the virus’ ability to replicate, thus killing it.

Prof. Weathers said the team members were “elated” when they first saw the results, especially since early results were underwhelming.

“Our first results were less than enthusiastic,” she said. “We made methylene chloride extracts of the plant, and when we tested it against the virus, there were toxic effects on the cells as well as the virus.”

The team speculated that this effect was probably from the solvent needed to dissolve the extracts. After a few more tests, the team decided to switch to a hot water extract. That is the way the plant was, and still is, used as a traditional medicine, and they thought that method could eliminate toxicity to the cells.

The hot water method worked. “There was essentially no cell toxicity but powerful antiviral activity. We were elated!” Prof. Weathers said.

Although they do not yet know exactly how or what in A. annua makes it so effective, they know that not only does it stop the virus replicating but it is also effective against COVID-19 variants, including delta and omicron.

The hot water (extraction) method worked. “There was essentially no cell toxicity but powerful antiviral activity. We were elated!” Prof. Weathers said.

The extracts further help subdue inflammation and alleviate the often-deadly “cytokine storm” that can happen with COVID-19.

Yet another finding is that the extracts can blunt fibrosis, also known as fibrotic scarring, which damages organs and tissue. Fibrosis can occur during a long viral infection and is implicated in “long COVID,” the name given to a range of new, returning or ongoing health problems that can follow an acute COVID-19 infection.

Impact of the Study

Despite the team’s exciting findings, the general response was mixed, said Prof. Weathers.

“We thought [our results] would be quickly explored further, tested in human clinical trials, and could provide a very cost-effective means to halt the virus,” she said. “We have been sadly disappointed in the response to our studies.”

Generally, when the public hears of our work, it is “very enthusiastic,” she said. “The medical community that is in tune with alternative medicine is also very interested, but they have little to no power.”

There has been some interest from academia, she said, and “I have no clue if anyone in the political sphere even knows about it.”

But the responses from public health agencies, health care leaders and drug manufacturers were virtual silence. “There is little to no interest by modern medicine, which is more connected to the pharmaceutical industry,” said Prof. Weathers.

One possible reason to shun “sweet wormwood” as a treatment for COVID-19 was the flood of “colorful” stories about cures for COVID-19, she said. “There were many crank cures touted early in the pandemic. That really hurt us in terms of anyone giving our work with a medicinal plant a more serious look.”

But she suspects the lack of apparent profitability is a bigger reason to ignore Artemisia annua as a treatment for COVID-19.

“This is a simple approach for treating a horrible disease; it is unlikely that any pharmaceutical company would look at it and develop it further,” she said. “There is no profit in it for them, and our health care systems are intimately tied to the pharmaceutical companies and profits, not inexpensive cures.”

Future Plans

Currently, the team is awaiting word from the National Institutes of Health about a small grant to help identify what in the plant makes it so potent. If funded, they hope that data they obtain will better inform and convince others to fund a larger clinical trial in humans.

Elsewhere, the World Health Organization has announced a trial of Artesunate—a derivative of artemisinin—and two other drugs on hospitalized COVID-19 patients.

Meanwhile, Prof. Weathers cautioned that, despite Artemisia annua’s apparent impact on COVID-19 during the tests, “it is not a vaccine.”

Instead, its role is “to be used in conjunction with vaccination or to buy time to get populations vaccinated.”


*Mark Smith is a journalist and author from the UK. He has written on subjects ranging from business and technology to world affairs, history, and popular culture for the Guardian, BBC, Telegraph, and magazines in the United States, Europe, and Southeast Asia.


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